The group were forced to turn back about 30 kilometres from the fields where the plane crashed.

Ms Bishop says the Australian Federal Police (AFP) mission at the crash site will remain unarmed but says the addition of Ukrainian parliamentary approval for weapons is simply a wise contingency plan.

"Part of that is to have the right, should it ever be necessary, to bring arms into the country for self-defence," Ms Bishop said.

"Now, I don't envisage that we will ever resort to that, but it is a contingency planning, and you would be reckless not to include it in this kind of agreement.

"But I stress our mission is unarmed because it is [a] humanitarian mission."

Ms Bishop said the Ukrainian president has assured her his troops were observing a 40-kilometre ceasefire zone around the crash site but there are numerous reports of ongoing and fierce battles close by.

She says the Australian-Dutch police contingent will try again to get to the site to search for human remains.

Prime Minister Tony Abbott says it is a frustrating situation.

"The separatists, the Russians, all of them ... they have all made a commitment to a ceasefire to provide humanitarian corridors for our police mission to go through," he told Macquarie Radio.

"It is high time that those commitments were honoured. I'll be making phone calls later today to try to see what we can do to make that happen.

"We owe it to the dead, we owe it to their loved ones to get them back and that is what we are determined to do."

In addition, international investigators will hold talks with Ukrainian forces and rebel fighters to try again to get access to the MH17 crash site.

Russian-speaking separatists have been desperately trying to halt the advance of Ukrainian troops and according to rebel leader Igor Strelkov, 30 of his men have been killed in the past 24 hours.

The delay in accessing the site has also frustrated Organisation for Security and Cooperation in Europe (OSCE) spokesman Michael Bociurkiw, who says the delays are unacceptable.

"It didn't get to the point where anyone was exposed to real danger," he told ABC News Breakfast.

"I mean, there were fairly heavy explosions or shelling nearby, but no debris flying our way and we did have the use, of course, of OSCE armoured vehicles.

"But it was so disappointing; 'unacceptable' is the word we used earlier when we spoke about this to the media, because so much preparation and groundwork had been done in consultation with the Ukrainian side and the rebel side, to make sure that we could reach our destination today.

"There should have been no question about our intentions, about our route, about our timing, and yet the safety situation kind of collapsed and we had to turn back."

Overnight, the European Union agreed to impose asset freezes and travel bans on business figures and entities closely associated with Russian president Vladimir Putin who have benefited from the Ukraine crisis.

It also agreed to "target further entities responsible for action against Ukraine's territorial integrity", an EU official said.